I have a Full Tilt 2-piece, and it's been great. For me, it's way better than a normal J&J due to the convenience of different sized tips, which makes it pretty easy to adapt it to your play, instead of having to buy 3 different barrels in different sizes. On mine, the bore is .687.

I would have kept using it, but I play at different fields all the time, with different-sized paint, so I got a Freak since it was more versatile for me. For now, it's in my gearbag if I don't feel like popping on my Freak.

As for the Apex attachment, it allows you to attach the Apex tip (sold separately from the adapter) from BT to the J&J. The Apex adds backspin, curve, etc. like the Flatline does for Tippmanns. With the Apex tip, you can do trick shots, too.